Abstract: A doctor blade head for coating a transfer roller includes a semi-cylindrical cavity to enable streamline fluid flow therethrough, and check plates at the inlet and outlet openings for permitting unidirectional flow into the inlet opening from said pump and out of the outlet opening toward the pump. An hydraulic accumulator acts as a fluid pressure and fluid velocity balancing device, and includes a rolling diaphragm piston moving in a cylinder that is connected to the inlet fluid path, with a spring impinging on the piston to absorb pressure surges and compensate pressure dropoffs.